Many electrophotographic output devices (e.g., laser printers, copiers, fax machines etc.) have traditionally required information about the print cartridge to be available to the output device such that the control of the machine can be altered to yield the best print quality and longest cartridge life.
Literature suggests several methods for detecting toner level in a laser printer. Most of these methods detect a low toner condition or whether toner is above or below a fixed level. Few methods or apparatus effectively measure the amount of unused toner remaining. As an example, some printers currently employ an optical technique to detect a low toner condition. This method attempts to pass a beam of light through a section of the toner reservoir onto a photo sensor. Toner blocks the beam until its level drops below a preset height.
Another common method measures the effect of toner on a rotating agitator or toner paddle which stirs and moves the toner over a sill to present it to a toner adder roller, then developer roller and ultimately the OPC drum. The paddle's axis of rotation is horizontal. As it proceeds through its full 360 degree rotation the paddle enters and exits the toner supply. Between the point where the paddle contacts the toner surface and the point where it exits the toner, the toner resists the motion of the paddle and produces a torque load on the paddle shaft. Low toner is detected by either 1) detecting if the torque load caused by the presence of toner is below a given threshold at a fixed paddle location or 2) detecting if the surface of the toner is below a fixed height.
In either method there is a driving member supplying drive torque to a driven member (the paddle) which experiences a load torque when contacting the toner. Some degree of freedom exists for these two members to rotate independently of each other in a carefully defined manner. For the first method 1) above, with no load applied to the paddle, both members rotate together. However, when loaded the paddle lags the driving member by an angular distance that increases with increasing load. In the second method 2), the unloaded paddle leads the rotation of the driving member, under the force of a spring or gravity. When loaded (i.e., the paddle contacts the surface of the toner), the driving and driven members come back into alignment and rotate together. By measuring the relative rotational displacement of the driving and driven members (a.k.a. phase difference) at an appropriate place in the paddle's rotation, the presence of toner can be sensed.
In the prior art, this relative displacement is sensed by measuring the phase difference of two disks. The first disk is rigidly attached to a shaft that provides the driving torque for the paddle. The second disk is rigidly attached to the shaft of the paddle and in proximity to the first disk. Usually both disks have matching notches or slots in them. The alignment of the slots or notches, that is how much they overlap, indicates the phase relationship of the disks and therefore the phase of the driving and driven members.
In many cartridges, a disk or an encoder wheel is provided (typically located on the side of the cartridge) whose function is to provide intelligence to the printer regarding the amount of new toner remaining in the toner hopper. This feature, along with the printed circuit board or “chip”, provides the printer and operator with vital information regarding the cartridge life, page yield, and other related data.
The chip is typically replaced every time a cartridge is remanufactured. The encoder wheel, however, is currently reusable. It is a mechanical device rotated by a gear drive that transfers information by its speed of rotation and special features on the wheel that are scanned as it rotates. The scanned information is used to determine the amount of toner remaining in the toner hopper and ultimately the life of the cartridge.
It may be desirable to limit the life of the encoder wheel and thereby restrict reuse of the cartridge. Disabling the encoder wheel prevents unauthorized reuse of the cartridge or will prevent a cartridge from being reused beyond its expected lifetime. The encoder wheel may be permanently disabled or temporarily disabled.